Using reflect to detect nil value

Question

I'm using the reflect package to create a re-usable JSON parser that maps JSON data to a particular struct at run-time.

I want it to detect when a particular required field is missing.

I create an variable "parsedInput" using:

parsedInput := reflect.New(reflect.TypeOf(exampleInputObject).Elem())

I've then used the JSON libraries to parse the data into that variable. I now want to traverse through the values to spot anything missing:

    for i := 0; i < parsedInput.Elem().NumField(); i++ {
            logger.Info("Field name was: " + field.Name)
            fieldType := fmt.Sprintf("'%v'", field.Type.Kind().String())
            logger.Info("Field type was: " + fieldType)
            interfaceValue := fmt.Sprintf("'%v'", parsedInput.Elem().Field(i).Interface())
            logger.Info("Interface value was: " + interfaceValue)

            //Look to see if the field is a null pointer.  If so, this could be an issue
            if (field.Type.Kind().String() == "ptr") && (parsedInput.Elem().Field(i).Interface() == nil) {
        //Do null pointer stuff here
    }
}

For the field that's missing, I see the log output

Field name was: MissingFieldName
Field type was 'ptr'
Interface value was '<nil>'

My code is never dropping into the null pointer logic however - what am I doing wrong?

Answer 1

As per comment above - I managed to solve this using built-in functions in the Reflect package - specifically by testing for:

Reflect.ValueOf(parsedInput.Elem().Field(i).Interface()).IsNil()